Post by Admin on Jun 21, 2022 19:29:28 GMT
Sex Bias and the Spread of Indo-European Languages
POWER IMBALANCES BETWEEN the sexes appear to have played a role in the spread of genes in numerous cases throughout pre-history. One of the most unexpected examples of how culture and technology combined to spread genes—and language—involves the Yamnaya, a horse-herding people who lived on the Eurasian steppe during the Bronze Age, 5,000 years ago. The story began to take shape in 2012, when Reich’s lab identified the genetic signature of a ghost population, one that no longer exists in unmixed form.
Reich and his colleagues had been assessing the relatedness of different groups of modern humans. When they compared Northern Europeans to Native Americans and Southern Europeans, each of whom have distinctive (but not necessarily functionally important) genetic changes at varying frequencies across their genomes, they observed a powerful statistical signal that Northern Europeans have “a massive contribution of genetic material from a population related to Native Americans.”
“We of course didn’t think that Native Americans sailed across the Atlantic. That seemed implausible,” he says. Instead, he and his colleagues proposed the existence of a population that no longer exists, the “Ancient North Eurasians.” “They would have lived in Siberia, or other parts of northern Eurasia, sometime before 15,000 years ago, and contributed to the ancestors of Native Americans before they crossed the Bering Land bridge into North America.” Then, some time later, genes of the descendants of the Ancient North Eurasians who had not crossed into North America somehow suddenly appeared in populations throughout Eurasia. “The signal” Reich recalls, “was very strong.”
“It was a weird observation,” he says, because the prevailing model from archaeology in 2012 “was that Europeans might very well be mixed between hunter gatherers who were the sole population in Europe before 8,500 years ago, and Anatolian farmers” who brought agriculture to Europe after that time. That theory rested on the reasonable—but as it turned out, incorrect—assumption that once farming was established in Europe, allowing highly efficient exploitation of local resources, it would have been difficult for any other group to make a major demographic impact. The discovery of genes related to Native Americans arriving in high proportion after the spread of farming was therefore very surprising. That’s why Reich and his close collaborator, research fellow in genetics Nick Patterson, had hypothesized the existence of this third source population, the Ancient North Eurasians.
The problem was that there were no modern populations living in Eurasia that were similar to the Ancient North Eurasians. Reich guessed that the Ancient North Eurasians had been largely displaced in the regions where they once lived by post-Ice Age migrations, and that their ancestry survived in higher proportion today only in Native Americans.
Then, in 2013, bones from a boy who lived near Lake Baikal around 24,000 years ago were sequenced by the Danish geneticist Eske Willerslev and his team, and these matched the genetic profile of the ghost population Reich’s group had hypothesized. Immediately, the hunt was on for the genetic signature of these mysterious people in samples of 5,000 year-old human bones and teeth gathered from archaeological sites throughout Eurasia. Gradually, Reich and his ancient-DNA-studying colleagues around the world zeroed in on one group: the Yamnaya.
The Yamnaya were horse-riding steppe pastoralists who shepherded vast herds of animals, setting up mobile wagon camps wherever they found fresh pasturage. Their lifestyle was made possible by the invention of the wheel a few centuries earlier, and the domestication of the horse. With those innovations, and the addition of dairying for sustenance, the vast and dry Eurasian steppe, which stretches thousands of kilometers from Hungary to Mongolia, became a superhighway—and the economic foundation of their success.
David Anthony, a professor of archaeology based at Hartwick College, now emeritus, had previously argued on the strength of linguistic evidence, as well as archaeological traces found on the grasslands of the steppe north of the Black and Caspian seas, that the Yamnaya were the best candidates for the spread of Indo-European languages. Their mobile way of life, he says, made their temporary settlements “archaeologically invisible.” Only their burial mounds, which, strikingly, included horses and wheeled vehicles, remain.
In his 2007 book, The Horse, The Wheel, and Language: How Bronze Age Riders from the Eurasian Steppes Shaped the Modern World, Anthony argued that whatever civilization had spread the language ancestral to the Indo-European languages (IEL) that are spoken today (including English), must have known about wheels and axles, pointing to common root words that change over time according to predictable phonological rules. And he noted that these languages were later spoken by militaristic, male-dominated societies with chariots, and that they shared similar mythologies, from Greece to India and Scandinavia.
Anthony had been searching for a civilization that could have spread a proto-Indo-European language for much of his career. When he sifted through the chronological, geographical, material, and linguistic evidence, only the Yamnaya fit all the criteria. And they generated subsequent migrations, undertaken by successor cultures, in the expected directions and sequences.
But even Anthony, now working in retirement with Reich as an associate of the department of human evolutionary biology, did not guess then that the Yamnaya transmitted more than just their language and culture. Their spread, as Reich and his ancient DNA colleagues have now documented, was accompanied by a massive, and previously unknown dissemination of Yamnaya genes.
“Their descendants,” Reich says, picking up the story, “continued to spread in the guise of another archaeological culture” known for their “corded ware” pots, achieving a “minimum 70 percent replacement of the population” then living in what is present-day Germany, and “within a hundred years,” through another successor “Beaker Bell” population, a “minimum 90 percent replacement of the population of Britain, just after Stonehenge had been built.” (Descendants of some of these groups expanded to the east as well, giving rise to the militaristic, chariot-riding Sintashta culture.)
The spread of steppe genes sometimes came with a strong sex bias, as Bronze Age populations with Yamnaya ancestry spread into South Asia (India) and across Western Eurasia. The male-lineage Y chromosome types carried by these groups were absent in India and Europe before the Bronze age, but are predominant in both places today, Reich says. Much of this ancestry is the result of what is known as a “star cluster,” when the genes of one very powerful man appear in millions of descendants. Reich estimates that 20 to 40 percent of Indian men and 30 to 50 percent of Eastern European men descend from a single man who lived between 6,800 and 4,800 years ago. In Iberia, Reich’s team uncovered further evidence of sex bias. By 4,000 years ago, genes spread by the descendants of the steppe people accounted for about 40 percent of the ancestry of those populations, with about 60 percent coming from the local inhabitants who had lived there previously. “But if you look at the Y chromosomes—the DNA that people get from their fathers—it was more or less 100 percent from the steppe. What this means is that the males coming in from this Eastern group had completely displaced the local males through some process.” Was it violence, or mate choice, or something else? Could disease have played a role? What happened is unknown, because these events took place before writing had arrived in this part of world.
POWER IMBALANCES BETWEEN the sexes appear to have played a role in the spread of genes in numerous cases throughout pre-history. One of the most unexpected examples of how culture and technology combined to spread genes—and language—involves the Yamnaya, a horse-herding people who lived on the Eurasian steppe during the Bronze Age, 5,000 years ago. The story began to take shape in 2012, when Reich’s lab identified the genetic signature of a ghost population, one that no longer exists in unmixed form.
Reich and his colleagues had been assessing the relatedness of different groups of modern humans. When they compared Northern Europeans to Native Americans and Southern Europeans, each of whom have distinctive (but not necessarily functionally important) genetic changes at varying frequencies across their genomes, they observed a powerful statistical signal that Northern Europeans have “a massive contribution of genetic material from a population related to Native Americans.”
“We of course didn’t think that Native Americans sailed across the Atlantic. That seemed implausible,” he says. Instead, he and his colleagues proposed the existence of a population that no longer exists, the “Ancient North Eurasians.” “They would have lived in Siberia, or other parts of northern Eurasia, sometime before 15,000 years ago, and contributed to the ancestors of Native Americans before they crossed the Bering Land bridge into North America.” Then, some time later, genes of the descendants of the Ancient North Eurasians who had not crossed into North America somehow suddenly appeared in populations throughout Eurasia. “The signal” Reich recalls, “was very strong.”
“It was a weird observation,” he says, because the prevailing model from archaeology in 2012 “was that Europeans might very well be mixed between hunter gatherers who were the sole population in Europe before 8,500 years ago, and Anatolian farmers” who brought agriculture to Europe after that time. That theory rested on the reasonable—but as it turned out, incorrect—assumption that once farming was established in Europe, allowing highly efficient exploitation of local resources, it would have been difficult for any other group to make a major demographic impact. The discovery of genes related to Native Americans arriving in high proportion after the spread of farming was therefore very surprising. That’s why Reich and his close collaborator, research fellow in genetics Nick Patterson, had hypothesized the existence of this third source population, the Ancient North Eurasians.
The problem was that there were no modern populations living in Eurasia that were similar to the Ancient North Eurasians. Reich guessed that the Ancient North Eurasians had been largely displaced in the regions where they once lived by post-Ice Age migrations, and that their ancestry survived in higher proportion today only in Native Americans.
Then, in 2013, bones from a boy who lived near Lake Baikal around 24,000 years ago were sequenced by the Danish geneticist Eske Willerslev and his team, and these matched the genetic profile of the ghost population Reich’s group had hypothesized. Immediately, the hunt was on for the genetic signature of these mysterious people in samples of 5,000 year-old human bones and teeth gathered from archaeological sites throughout Eurasia. Gradually, Reich and his ancient-DNA-studying colleagues around the world zeroed in on one group: the Yamnaya.
The Yamnaya were horse-riding steppe pastoralists who shepherded vast herds of animals, setting up mobile wagon camps wherever they found fresh pasturage. Their lifestyle was made possible by the invention of the wheel a few centuries earlier, and the domestication of the horse. With those innovations, and the addition of dairying for sustenance, the vast and dry Eurasian steppe, which stretches thousands of kilometers from Hungary to Mongolia, became a superhighway—and the economic foundation of their success.
David Anthony, a professor of archaeology based at Hartwick College, now emeritus, had previously argued on the strength of linguistic evidence, as well as archaeological traces found on the grasslands of the steppe north of the Black and Caspian seas, that the Yamnaya were the best candidates for the spread of Indo-European languages. Their mobile way of life, he says, made their temporary settlements “archaeologically invisible.” Only their burial mounds, which, strikingly, included horses and wheeled vehicles, remain.
In his 2007 book, The Horse, The Wheel, and Language: How Bronze Age Riders from the Eurasian Steppes Shaped the Modern World, Anthony argued that whatever civilization had spread the language ancestral to the Indo-European languages (IEL) that are spoken today (including English), must have known about wheels and axles, pointing to common root words that change over time according to predictable phonological rules. And he noted that these languages were later spoken by militaristic, male-dominated societies with chariots, and that they shared similar mythologies, from Greece to India and Scandinavia.
Anthony had been searching for a civilization that could have spread a proto-Indo-European language for much of his career. When he sifted through the chronological, geographical, material, and linguistic evidence, only the Yamnaya fit all the criteria. And they generated subsequent migrations, undertaken by successor cultures, in the expected directions and sequences.
But even Anthony, now working in retirement with Reich as an associate of the department of human evolutionary biology, did not guess then that the Yamnaya transmitted more than just their language and culture. Their spread, as Reich and his ancient DNA colleagues have now documented, was accompanied by a massive, and previously unknown dissemination of Yamnaya genes.
“Their descendants,” Reich says, picking up the story, “continued to spread in the guise of another archaeological culture” known for their “corded ware” pots, achieving a “minimum 70 percent replacement of the population” then living in what is present-day Germany, and “within a hundred years,” through another successor “Beaker Bell” population, a “minimum 90 percent replacement of the population of Britain, just after Stonehenge had been built.” (Descendants of some of these groups expanded to the east as well, giving rise to the militaristic, chariot-riding Sintashta culture.)
The spread of steppe genes sometimes came with a strong sex bias, as Bronze Age populations with Yamnaya ancestry spread into South Asia (India) and across Western Eurasia. The male-lineage Y chromosome types carried by these groups were absent in India and Europe before the Bronze age, but are predominant in both places today, Reich says. Much of this ancestry is the result of what is known as a “star cluster,” when the genes of one very powerful man appear in millions of descendants. Reich estimates that 20 to 40 percent of Indian men and 30 to 50 percent of Eastern European men descend from a single man who lived between 6,800 and 4,800 years ago. In Iberia, Reich’s team uncovered further evidence of sex bias. By 4,000 years ago, genes spread by the descendants of the steppe people accounted for about 40 percent of the ancestry of those populations, with about 60 percent coming from the local inhabitants who had lived there previously. “But if you look at the Y chromosomes—the DNA that people get from their fathers—it was more or less 100 percent from the steppe. What this means is that the males coming in from this Eastern group had completely displaced the local males through some process.” Was it violence, or mate choice, or something else? Could disease have played a role? What happened is unknown, because these events took place before writing had arrived in this part of world.